Directing groups ketone

DG = directing group ketone, aldehyde, amide, phenol, imine, oxazoles, imidazoles, etc. 

Styrenes [103], conjugated aT-dienes [107], and aT-enynes [108] are also epoxidized with ketones 57 in high ees (Table 5, entries 9-14). No isomerization of the epoxides was observed therefore only c/x-epoxides were obtained from cis-olefins. Alkenes and alkynes appear to be effective directing groups to favor the desired transition states T and V (Fig. 19). 

Another example of the superiority of the alkoxy group as a directing group was reported by Johnson in his synthesis of enantiomericaUy pure cyclopropyl ketones after auxiliary cleavage (equation 56). In that case, the product resulting from a sulfoximine directed cyclopropanation was never observed. 

The drawing of the first two molecules gives you the clue that, after stereospecific tin-lithium exchange (pp. 1306-8), the vinyl-lithium attacks the carbonyl group direct. The ketone in the first product is formed by hydrolysis of the enol ether (pp. 540-1) in the work-up. 

The metaiation of heterocycles is possible without the aid of a directing group. This type of reaction is most common in the ir-excessive heterocycles, and is most important for thiophenes. For nitrogen heterocycles, examples of unactivated lithiation of ir-excessive azoles have been reported, and are summarized below. ir-Deficient heterocycles such as pyridine are resistant to unactivated lithiation, although pyridine can be metalated with low regioselectivity using butylsodium. Pyridines also form weak complexes with fluoro ketones the complex of 4-r-butylpyridine and hexafluoroacetone can be lithiated and added to benzaldehyde in 60% yield. ... 

When one of the carbonyl carbons is at the oxidation level of acid (as in a 2-pyrone), then the product, reflecting this oxidation level, is a 2-pyridone. Similarly, 4-pyrones react with ammonia or primary amines to give 4-pyridones and the bis-enamines which can be obtained directly from ketones by condensation on both sides of the carbonyl group with DMFDMA, produce 4-pyridones on reaction with primary amines. When one of the carbonyl units is actually a nitrile, then an amino-pyridine results. ... 

Substituted benzaldehydes, with a formyl substituent as directing group, were selectively arylated at their ortho-position with aryl bromides as electrophiles in the presence of palladium(O) catalysts [50]. The use of a ruthenium complexes within a cooperative multi-catalytic system [51] altered the chemoselectivity dramatically [52]. Thus, reactions of 8-formylquinoline (39) with iodoarenes proceeded regioselectivity at the formyl group itself to give the corresponding ketones in moderate to very good yields (Scheme 9.15) [52],... 

The reaction of diethyl oxalate with ketones in the presence of sodium ethoxide, or other bases, has been used extensively examples are given in Scheme 66. Reaction may occur with esterketone ratios of 1 1, 2 1, or 1 2, but only the 1 1 case finds substantial use in modem synthetic practice. Frequently the a-oxalyl ketone is thermally decarbonylated to give the 3-heto ester.An early example of this was provided by Bachmann s synthesis of equilenin. The mechanism of this reaction has teen examined labeling studies showed that it was the ester carbonyl that was eliminated. The intact oxalyl group has teen used as a directing group in steroid methylation while, more recently, 2-oxalylcyclohexanone has provided a route to (R)-(-)-hexahydromandelic acid (Scheme 67). The products of acylation of suitable acyclic ketones can cyclize to form (enolic) cyclopentane-1,2,4-triones (equation 39). ... 

Matsuda et al. have studied the hydroxyl group directed intermolecular ketone-olefin coupling reactions, induced by Sml2, between a-hydroxy ketones and a,P-unsaturated esters or nitriles (Scheme 30). It was noted that reactions... 

Carbonyl electrophiles can suffer competing enolization (Table 1). With the methoxymethyl directing group, reactive carbonyl compounds including aldehydes [24, 28, 49, 56, 69-72], acid chlorides [17, 24, 34, 44, 56, 57, 73-76], anhydrides [77,78], esters [22,24,79-81], amides [22,28,82-84] and several ketones [19, 22, 28, 70, 85, 86] were reported (Eq. 7). Others include phenyl isocyanate [54,78,87],benzonitrile [55], and imine derivatives [28]. 

---